The present invention relates to a display device for use in AV (audio visual) equipments or OA (office automation) equipments.
Recently, there has been an increasing demand for home TV sets representing AV equipments and display devices for use in OA equipments of improved characteristics such as light weight, thin structure, low power consumption, high definition performance and large screen, etc. To meet these demand, the development of display devices such as a CRT (cathode ray tube) display, an LCD (liquid crystal display), a PDP (plasma display panel), an EL (electro luminescent) display, and an LED (light emitting diode) display has been made to achieve improved characteristics thereof, and some of the display devices of improved characteristics have already been used in practical applications.
Especially, the home AV equipments are more and more demanded for amusement purposes. The current home AV equipments"" market also shows that a consumer""s demand is gradually shifted to a larger screen thanks to a reduction in per inch cost. The introduction of the stereophonic sound system also requires home AV equipments to have large screens.
In the business world, there has been an increasing demand for display devices of improved characteristics that offer high visibility effect with easy handling, such as improved brightness not only in still image but also in moving image, that can be suitably used in presentation performance using a computer, etc. To respond to such demand for the described improved characteristics in the business world, a development of display devices of larger screen has been still more expected.
Among such display devices, liquid crystal display devices can be installed even in a small space with ease because of its beneficial features being lighter weight, narrower width, thinner structure than other display devices. Moreover, for other beneficial characteristics of low power consumption and being evolvable into full-color display with ease, the liquid crystal display"" market has been expanded in various fields recently and the development of large-screen liquid crystal display devices has been more strongly demanded than other display devices.
However, when the screen of the liquid crystal display is upsized, as a defect image becomes more noticeable under the same resolution per screen, improvements in the resolution is necessary to achieve quality images of a video source. In the liquid crystal display device, an image is formed by display elements that are integrally formed and can be controlled independently, and thus to increase the number of display elements is inevitable to achieve an improved resolution.
However, the reduction in percent defective of each display element in the manufacturing process already faces the limit, and a significant progress is difficult to be expected.
Namely, to produce a greater number of display elements to meet the demand for the liquid crystal display device of a large screen would accelerate a drop in yield of the display device as a whole. Thus, it would be difficult to mass-produce the liquid crystal display device of a large screen which offers high quality images, and a cost for such liquid crystal display device remains too high.
To overcome the described difficulties, as shown in FIG. 2 of the present embodiment, a method of upsizing a screen using a so-called multi-panel display system has been proposed wherein an image is displayed on a large screen formed by joining plural liquid crystal display panels together. By adopting such system, even with the same percent defective of a single display element, as the defect is dispersed entirely on the display device, an overall improvement of a yield of the liquid crystal display device of a large screen which offers high quality images can be achieved while suppressing an increase in per unit area cost.
When forming a liquid crystal display device of a multi-display system, for example, as shown in FIG. 12(a), liquid crystal panels 52 are joined together. Specifically, the plural liquid crystal panels 52 are joined together so as to be adjacent to one another on a surface of a reinforcing substrate 53 to enable a liquid crystal display device of a still larger screen.
However, when joining plural liquid crystal display panels 52 together to enable such liquid crystal display device of a large screen, if an end surface portion 52c of the liquid crystal panel 52 contacts a medium of different index of refraction (air, etc.), light refraction would occur. Besides, if the end surface portion 52c becomes coarse in the manufacturing process, refraction and scattering of light would occur, thereby presenting the problem that the joint between the liquid crystal panels 52 stands out.
In consideration of the above problems, it is preferable that a hardened bonding agent used in bonding the liquid crystal panels 52 to the reinforcing substrate 53 has the same index of refraction as a hardened bonding agent used in joining the liquid crystal panels 52 together and that the index of refraction of these hardened bonding agents is substantially equal to the index of refraction of the reinforcing substrate 53 and substrates which constitute the liquid crystal panel 52, etc. By arranging so, refraction and scattering of light can be suppressed.
However, as shown in FIG. 12(b), in the case of adopting the bonding agent 59 under the described condition, a crack 59a may generate along the edge of the liquid crystal panels 52. This is because along an edge 52a (see FIG. 12(a)) of the liquid crystal panels 52, as stress concentrates by the curing shrinkage of the bonding agent 59, a crack 59a may be generated or may be expanded even with a small impact. When light passes through such crack 59a, light scattering would occur, which again makes the joint between the liquid crystal panels 52 stand out.
With the described curing shrinkage, a partial pealing 59b occurs between the end surface portion 52c of the connected part of the liquid crystal panels 52 and the bonding agent 59, which would cause the light scattering.
Additionally, when the face precision of the end surface portion 52c is low, since the bonding agent 59 is not spread entirely on the irregularity of the end surface portion 52c, fine bubbles may remain in the space between the end surface portion 52c of the liquid crystal panel 52 and the bonding agent 59. Such fine bubbles remaining in the space may again cause a scattering of light.
Namely, to display a natural image on a large screen, it is required to prevent an occurrence of light scattering, for example, by preventing a generation of the crack 59a, the peeling 59b or bubbles as this makes the joint between the liquid crystal panels 52 noticeable.
It is therefore an object of the present invention to provide a display device of a large screen formed by joining plural panels together which offers a natural image without generating light scattering at a connected part of the panels.
To fulfill at least the above-mentioned object, an example display device in accordance with the best presently contemplated embodiment of the present invention includes:
plural display panels, adjoining display panels being connected with each other by means of a bonding agent so as to have a single display screen,
wherein at least one edge portion of an end surface of a connected part of each display panel is chamfered.
In the display device having the described arrangement, a space between adjoining display panels is filled with the bonding agent, and when joining the display panels together, a concentration of the internal stress caused by a curing shrinkage of the bonding agent is suppressed at the chamfered edge portion. Namely, at such edge portion, as a maximum value of the internal stress becomes smaller than an intermolecular bond strength of the bonding agent, a generation of cracks around the edge portion can be prevented. Therefore, as light scattering caused by such cracks can be reduced, a desirable display device of a large screen having an excellent visibility in which a joint of the display panels is not noticeable can be achieved.
In furtherance of the above-mentioned object, an example of the display device of the present invention includes plural display panels, adjoining display panels being connected with each other by means of a bonding agent, so as to have a single display screen, wherein an interval between the adjoining display panels is not more than 50 xcexcm.
According to the described arrangement, as the interval between the adjoining display panels is selected to be not more than 50 xcexcm, the absolute value of the volumetric shrinkage due to the curing shrinkage of the bonding agent can be made smaller. This enables a value of the internal stress generated in the hardened bonding agent to be smaller than the intermolecular bond strength of the hardened bonding agent, thereby preventing a generation of cracks due to the hardened bonding agent around the edge portion. In the meantime, the internal stress is smaller than the bond strength between the bonding agent and the display panels, thereby preventing a generation of a peeling. As this prevents light scattering caused by cracks or a peeling at the connected part of the display panels, a desirable display device of a large screen having an excellent visibility in which a joint of the adjoining display panels is not noticeable can be achieved.
To achieve the above-mentioned object, another example of the display device in accordance with the present invention includes plural display panels, adjoining display panels being connected with each other by means of a bonding agent, so as to have a single display screen, wherein the hardened bonding agent has a flexural modulus of elasticity of not more than 4,000 kgf/cm2.
According to the described arrangement of the display device, even under the same curing shrinkage of the bonding agent, the internal stress generated by the curing shrinkage of the bonding agent is absorbed by the elasticity (flexibility) of the bonding agent. Namely, as the maximum value of the internal stress becomes smaller than the intermolecular bond strength of the hardened bonding agent, a generation of cracks due to the hardened bonding agent around the edge portion can be prevented. Furthermore, as the internal stress can be made smaller than the bond strength between the bonding agent and the display panels, a generation of peelings can be prevented. Namely, as light scattering due to cracks or peelings generated at the connected part of the display panels can be suppressed, a desirable display device of a large screen having an excellent visibility in which a joint of the display panels is not noticeable can be achieved.
To achieve the above-mentioned object, a display device in accordance with the present invention includes: plural display panels, adjoining display panels being connected with each other by means of a bonding agent, so as to have a single display screen, wherein an end surface portion of a connected part of each display panel has a cut surface finishing precision of not more than 2 xcexcm.
According to the described arrangement of the display device, as the bonding agent can be more efficiently spread on the end surface portions of the display panels, generation of bubbles in a space between the end surface portions of the connected parts and the bonding agent can be prevented. Namely, the improved wettability permits display panels to be joined together without having residual bubbles remaining on the interface with the bonding agent, thereby preventing light scattering caused by such bubbles. As a result, a desirable display device of a large screen having an excellent visibility in which a joint of the display panels is not noticeable can be achieved.
To fulfill the above-mentioned object, a display device in accordance with the present invention includes plural display panels, adjoining display panels being connected with each other by means of a bonding agent, so as to have a single display screen, wherein an end surface of a connected part of each display panel has a cut surface positioning precision of not more than 10 xcexcm.
In the display device of the described arrangement, the width of the connected part of the display panels can be reduced. Specifically, the width of the connected part of the display panels can be reduced to not more than 20 xcexcm. Therefore, even under fluctuating index of refraction of the bonding agent, an adverse effect on color, or distortion of an image formed by light passing through the connected part of the display panels can be suppressed, thereby achieving a desirable display device of a large screen having an excellent visibility in which a joint of the display panels is not noticeable.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.